The purpose of this investigation is to learn more about the significance of polymorphonuclear neutrophilic leukocytes (PMNs) in the pathogenesis of periodontal disease. Large numbers of PMNs come into direct contact with the heterogenous microbial plaques which are thought to be the principal etiologic agents in the disorder. But very little is known about whether PMNs serve as mediators of antibacterial defense and/or inflammatory tissue injury in the disease. PMNs will be secured at different intervals over 30 days during the development of experimental gingivitis in humans. Cells will be assessed for their relative capacities to liberate lysosomes in response to autologous supragingival plaque, to respond to chemotactic stimuli, and to phagocytose and kill representative plaque bacteria, etc. The effect(s) of autologous fresh and heated (56 degrees C, 30 min.) serum on these phenomena will be assessed in these experiments. Similarly, PMN function will be evaluated in individuals with moderate to advanced periodontal pathology before and after they have received treatment for the disease. Information from these studies should enable us to construct functional profiles of PMN responsiveness in experimental gingivitis and established periodontal disease and may provide new insight into the role of PMNs in the disease. Additional studies will be undertaken to define the mechanisms and consequences of PMN-PMN and PMN-lymphocyte interactions in the pathogenesis of periodontal inflammation. PMN-derived soluble products will, for example, be preincubated with plaque bacteria; the functional responsiveness of PMNs to such altered stimuli will then be analysed. We will also determine whether PMNs contain and secrete substances which stimulate lymphoid blastogenesis and lymphokine production. Likewise, we will ascertain if lymphoid-derived products modulate PMN function to challenge with plaque bacteria. These experiments will help give us a better understanding of the potential significance of cell-cell interactions in inflammatory lesions.